1. Field of the Invention
The present invention relates to an electronic keyboard musical instrument. Especially the present invention relates to a technique having a preferred resonating sound generation unit for simulating a string resonating sound, which is generated such as when a damper pedal is manipulated in an acoustic piano.
2. Discussion of Background
An acoustic piano has a damper pedal and dampers holding strings. A manipulation of the damper pedal spaces the dampers from the strings. This allows not only an actually-struck string but all the other strings to resonate. Accordingly, such electronic keyboard musical instruments as electronic pianos and electronic organs also require a function to simulate the string resonating sound by the manipulation of the damper pedal.
For example, such electronic keyboard musical instruments employ a method in which these instruments record both a normal piano sound with no manipulation of the damper pedal and a piano sound including a resonating sound under a manipulation of the damper pedal. These instruments store pieces of waveform data of such piano sounds so as to select a suitable piece of waveform data according to the presence/absence of the damper pedal manipulation for generation of a musical tone.
These instruments also use a system in which they record a piano sound including the resonating sound under the manipulation of the damper pedal, remove only a harmonic tone from the recorded piano sound to generate a resonating sound component in order to store its waveform data. These instruments then generate the resonating sound component together with a normal musical tone by using a plurality of channels when the damper pedal is manipulated.
As one of examples, Japanese Unexamined Patent Application Publication No. H09-127941 discloses an electronic keyboard musical instrument including a resonating sound musical tone waveform data memory for storing waveform data of musical tone which represents only a resonating sound of a fundamental tone. This instrument is configured to control amplitude of waveform data which is readout from the resonating sound musical tone waveform data memory in accordance with an instruction by the damper pedal.
Furthermore, there is also a method that rather than generating musical tones based on the pieces of waveform data stored in advance, configures a resonating sound generation unit using a digital signal processor (DSP) to output a signal for generating the resonating sound through the resonating sound generation unit only when the damper pedal is manipulated.
However, the system that uses a plurality of channels to generate the resonating sound component together with the normal musical tone has a problem in that its predetermined number of channels causes sound breaks due to lack of the channels in the case where the number of emitted sounds increases.
On the other hand, the system (the resonating sound generation unit) in which DSP performs arithmetic operations to generate the resonating sound has problems that the necessity of many operations increases the scale of the system, and that, in the case of the resonating sound generation unit with external memories (delay memories) and feedback loops in use, the accurate pitch control becomes complicated in the high register. In other words, DSP often uses the integer arithmetic for a delay amount corresponding to a pitch in order to decrease the arithmetic operations. However, the higher the register becomes, the larger the rounding error becomes. It has emerged as a problem that the accurate pitch control becomes impossible.
The present invention has been made to solve the above-described problems and it is an object of the present invention to provide an electronic keyboard musical instrument capable of generating the resonating sound which allows the accurate pitch control in the high register without sound breaks.